Engine systems may utilize recirculation of exhaust gas from an engine exhaust system to an engine intake system (intake passage), a process referred to as exhaust gas recirculation (EGR), to reduce regulated emissions. An EGR system may include various sensors to measure the EGR. As one example, the EGR system may include an intake gas constituent sensor which may be employed to measure oxygen to determine the proportion of combusted gases in an intake passage of the engine. The output of such a sensor may vary as a function of pressure at the sensor location; for example, the output may vary as a function of the diffusion coefficient of the sensor. Due to manufacturing variability, for example, the diffusion coefficient may vary between sensors. As such, accuracy of the sensor output may be reduced.
The inventors herein have recognized the above issue and have devised an approach to at least partially address it. Thus, a method for a gas constituent sensor in an engine system which includes an EGR system is disclosed. The method includes, based on a gas constituent sensor output and a pressure sensor output, generating a correction while exhaust gas recirculation is off. The method further includes adjusting an amount of EGR based on the gas constituent sensor output and the correction while the exhaust gas recirculation is on.
The gas constituent sensor may be an intake gas constituent sensor, for example, which outputs an intake oxygen concentration. By generating the correction while the EGR is off, pressure variations in the intake system due to EGR may be reduced. Further, because the EGR is off, air flowing through the intake passage is substantially ambient air for which the oxygen concentration is known. As such, the correction for the gas constituent sensor may be obtained with a greater accuracy. Once the correction is applied to the sensor output, the amount of EGR is adjusted such that engine operation may be improved. For example, when the EGR is adjusted based on the corrected sensor output, the engine may operate with an air fuel ratio closer to a desired air fuel ratio.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.